Topic 2.2 - Comets & Meteors Flashcards Preview

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Flashcards in Topic 2.2 - Comets & Meteors Deck (29)
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1
Q

What are comets?

A

Cometa are balls of rock and ice that form tails in the course of their highly-elliptical orbits around the Sun

2
Q

What are the comets two types of tail called?

A

Dust and Ion

3
Q

What is the difference between a dust tail and an ion tail?

A

An ion tail points in the opposite direction to the Sun whereas a dust tail follows the way the comet is moving

4
Q

When do comets develop tails?

A

As they approach the Sun

5
Q

What is a short period comet?

A

They have periods of less than 200 years and originate from the Kuiper belt. They’re 30-50 AU from the Sun

6
Q

What is a long period comet?

A

They have periods of more than 200 years and can be up to millions. They originate from the Oort Cloud which is brought 50,000 AU from the Sun

7
Q

What do observations of long period comets indicate?

A
  1. Their paths around the sun are in either sense (clockwise or anticlockwise)
  2. Orbits are often highly inclined to the ecliptic
  3. The high percentage of them originate at vast distances (typically 50,000 AU) from the sun
8
Q

What happens to a comet as it approaches the Sun?

A

Its temperature rises and gas and dust form an extremely rarefied spherical coma that surround the nucleus, up to 100,000 km across

9
Q

Describe an ion tail.

A

It’s blue-coloured and straight, consisting of atoms and molecules of gas (most carbon monoxide) that have been ionised by the solar wind; when they de-excite, atoms emit light by fluorescence

10
Q

Describe a dust tail.

A

It’s lighter-coloured, shorter, broader and slightly curved and produced by radiation pressure that pushes particles out of the nucleus; this tail of dust and grit shines reflecting sunlight and its curvature is due to the individual dust particles following their independent solar orbit

11
Q

What is a meteoroid?

A

Small rocky (with maybe some iron-nickel content) irregular lumps of debris in the Solar System that range in size from micrometers to several metres

12
Q

Where do meteoroids originate from?

A

Some are broken fragments of colliding asteroids whereas others formed through impacts with the surface of the moon or mars-they all orbit the Sun at speeds of up to 40 km/s. A number of meteoroids originate from the dust tails of comets, forming groups called meteoroid streams and are sources of meteor showers

13
Q

What’s a meteor?

A

Many meteoroids intersect the Earth’s orbit. When they enter our atmosphere, friction causes the meteoroid and surrounding air to heat up producing a short streak of incandescent light - a meteor or shooting star

14
Q

What is a fireball?

A

A meteor with a magnitude of -3 or brighter

15
Q

What is a meteorite?

A

A part of a meteoroid that survives its passage through the atmosphere and lands on the Earth’s surface

16
Q

What allows astronomers to classify meteorites into 3 major categories?

A

Geochemical analysis

17
Q

What are the 3 major categories that meteorites are classified in?

A

Stones, irons and stoney-irons depending on the ratio of rock to metal

18
Q

What is the radiant?

A

The point where meteors seem to diverge from this point in the sky even though they are actually travelling parallel

19
Q

How is a meteor shower named?

A

It is names after the constellation in which the radiant is found

20
Q

What is an NEO?

A

There are a number of asteroids and comets with orbits that bring them close to that of Earth. Near Earth Objects (NEOs) are those whose trajectory might bring them closer to Earth than 0.3 AU

21
Q

In October 2008, how many NEOs were known?

A

5600

22
Q

What is a PHO?

A

A significant proportion of NEOs have projected orbits that might bring them even closer to our planet. These are Potentially Hazardous Objects (PHOs) and they have orbits that bring them closer than 0.05 AU to us.

23
Q

In October 2008, how many PHOs were identified?

A

1000

24
Q

Name 3 examples of collisions in our Solar System between astronomical bodies.

A
  1. The Moon, several planets and asteroids are covered with impact craters
  2. The planets Venus and Uranus rotate on their axis in unusual ways (‘backwards’ and ‘sideways’ respectively). Both are thought to be a consequence of gigantic collisions early in the Solar Systems history
  3. The Chicxulub Crater straddling the coast of Mexico (this collision is believed to have caused the mass extinction of dinosaurs 65 million years ago)
25
Q

What size PHOs pose the biggest threat?

A

PHOs with a diameter of larger than 1 km - these are considered to have enough impact energy to cause a catastrophe on a global scale

26
Q

What is the Torino scale?

A

It uses numbers to from 0 to 10 based on the likelihood of a collision and the estimated kinetic energy of the impactor. Numbers 0 to 1 indicate likely misses or collisions with objects so small that no damage would ensue. However at the other end of the scale, numbers 8, 9 and 10 refer to what would amount to certain collisions, capable of inflicting localised, regional or world-wide devastation (in the form of land destruction, tsunamis or global climate change that could threaten the future civilisation). It’s in order to categorise impact hazards and communicate potential risks to the public

27
Q

What is a micrometeorite?

A

A meteorite that can land to the surface without lighting up- becoming incandescent

28
Q

If a PHO hit earth what could happen?

A
  1. So much dust and debris would be thrown up into atmosphere there would be no sunlight - lowering temperatures and perhaps extincting life
  2. Super tsunami
  3. Disrupt Earth’s tectonic plates
29
Q

At what speed do meteoroids orbit then sun?

A

40 km/s